Income Taxes - Provision for income taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income tax expense:
Currently payable	$ 7,730	$ 7,130	$ 5,476
Deferred income tax benefit	(720)	(688)	(321)
Total income tax expense	7,010	6,442	5,155
Expected tax expense, at the U.S. federal statutory income tax rate of 21%	$ 6,217	$ 5,736	$ 4,562
U.S. federal statutory income tax rate	21.00%	21.00%	21.00%
State income taxes	$ 786	$ 827	$ 692
Other, net	7	(121)	(99)
Total income tax expense	7,010	6,442	5,155
Disclosure Other Comprehensive Income Loss Tax Effects Allocation to Component Of Other Comprehensive Income Loss [Abstract]
Other comprehensive income (loss) related to marketable securities	$ 0	$ 0	$ 0